Very sudden lower back pain, and sort of can't move?

[sarahve1]

Hello, I'm new here, I'm 18 years old and a girl. For the last couple of months, I've had a recurring problem with my back. Regularly, when I make a hollow back (to stretch out for example), a sudden, sharp pain sets in - in my lower back - when I try to move it back to normal. I have to stay in this hollow position for a couple minutes, before I can slowly (and painfully) move out it. After that, making either a rounded or hollow back both gives that sharp pain again. Oftentimes, I also cannot twist my back. I can do this all again after a couple of minutes. Is there anybody that knows what this might be? Thank you in any case!